Method and apparatus for maintaining temperature and humidity constant



Nov. 3, 1953 T. EICHMANN 2,657,543

METHOD AND APPARATUS FOR MAINTAINING TEMPERATURE AND HUMIDITY CQNSTANTFiled Oct. 8, 1948 N I awe/Mm:

m (BAR ATTORNEYJ Patented Nov. 3, 1953 METHOD AND APPARATUS FORMAINTAIN- ING TEMPERATURE AND HUMIDITY CON- STANT Theophil Eichmann,Berne, Switzerland, assignor to George B. Scarlett, Kennett Square,Chester County, Pa.

Application October 8, 1948, Serial No. 53,394

I 7 Claims.

1 This invention relates to methods and apparams for maintainingtemperature and humidity constant; and the nature and objects of theinvention will be readily recognized and understood by those skilled inthe arts involved in the light of the following explanation of thepreferred method and the steps thereof of my invention and of thedetailed description and explanation of the accompanying drawingillustrating what I now consider to be a preferred improvement andarrangement of apparatus of my invention capable of operation to carryout and perform such preferred method.

This invention relates particularly to a method of .keeping thetemperature and the humidity constant in the air of a cold chamber bymeans of a refrigerating machine. The method according to the inventionconsists in the feature that the refrigerating machine, as well as anaircooled condenser and a water-cooled condenser connected in paralleltherewith, are controlled by a thermostat and a hygrostat in such a waythat the evaporator and the water-cooled condenser are set in operationby the thermostat, and, after attainment of a predetermined temperatureand release by the thermostat, the evaporator and the air-cooledcondenser are set in operation by the hygrostat, until the thermostatinterrupts the action of the hygrostat and switches on the coolingoperation again. insofar as the predetermined value of the humidity ofthe air has not already been reached previously by the hygrostat.

Apparatus of my invention for carrying out the method thereof isillustrated more or less schematically by Way of example in theaccompanying drawing.

Referring to the drawing, the apparatus of the example includes anair-cooled condenser I in a passage l5, and a water cooled condenser 2connected in parallel therewith by the hot, compressed gas supply linela and the condensate return line lb. An evaporator 3 is, in thisinstance, located in the passage l5 and is connected with the suctionintake side of a compressor 4. by the suction or return gas line 3a. Aswill be understood by those skilled in the art, both condenser I andevaporator 3 are in heat exchange relation with the air of the chillroom. The compressed gas discharge or pressure line 2a connects thedischarge side of compressor 4 with condensing coil 2b of condenser 2.The compressed gas line la to the air cooled condenser is connected toand receives hot, compressed gases fromv the discharge line 2a from thecompressor 4 just in advance of the condenser 2.

The water cooled condenser 2 is Supplied with cooling water by a supplyline la, and water is discharged from the condenser by the dischargeline 1b, in the usual manner of the conventional water cooled condensersfamiliar to the art. The cooling evaporator 3 receives condensedrefrigerant for expansion therein, through a con densate supply line 31)which has its intake end in a condensate reservoir or tank IS, in accordance with conventional practice. Condensed refrigerant is supplied tothe reservoir l6 by a supply line 2c connected to the discharge end ofcondensing coil 2b and discharging into reservoir- IS. The condensateline lb from the air cooled condenser I is, in this instance, connectedinto line 20 for the return of condensate from air cooled condenser l tothe reservoir I6. I An electricallycontrolled solenoid type valve 5 isconnected into the condensate line 20 between condenser 2 and thecondensate reservoir H; for controlling flow of condensate through thisline. An electrically controlled solenoid type of valve 5 is connectedinto the condensate return line lb between the air cooled condenser land the reservoir It for opening or shutting ofl this line to flow ofcondensate therethrough.

In the cooling operation or cycle of the apparatus, the cooled vaporsare sucked out of the evaporator 3 by compressor 4 through the vaporreturn line 3a, compressed by the compressor, condensed in the condenser2 and then returned to the evaporator 3 through line 20, reservoir l6and line 3b, all in accordance with the usual refrigerating or coolingcycle familiar in the art. In the operation of the refrigerating cyclethe valve 5 in line 20 is open while the valve 6 in line lb from the aircooled condenser l is closed. In the heatpumping or air conditioningoperation of the apparatus, the valve 6 is opened while the valve 5 isin a partially closed or throttled position, so that the hot, compressedgases from the compressor 4 are discharged through line lav through theair cooled condenser l and returned as condensate through line lb to thereservoir IS.

The compressor 4 is power driven by an electric motor I! in the usualmanner, this motor being in this instance supplied with operatingcurrent through a three-phase power circuit comprised by the circuitlines R-S-T. In this circuit there is located and connected the usualmotor controlling and protecting contactor unit l8, as will be familiarto those skilled in the art. The operationv of the compressor and theoperation and control of the solenoid valves 5 and 6 is effectedautomatically through an electrical control system which includes athermostat 8 associated with a control or master relay 9, and ahygrostat I2 associated with a control relay II. The thermostat 8 andthe hygrostat I2 are, of course, located in the chill room.

The thermostat .8, which as shown schematically may be of any of thewell-known mercury tube types, is connected with the power circuit R-S-Tby the controlling circuit line 8a, and is connected to the master relay9 by a circuit line 8b for control of the cooling cycle. The masterrelay controls a circuit therefrom to the solenoid valve 5 whichincludes the circuit line 541. The relay 5 also includes and controls acircuit for effecting operation of the contactor I8 for controllingoperation of the compressor 4 by the motor I'I, such circuit beingconstituted by the circuit line IBa. And the relay 9 also includes acontrolling circuit for operating the fans II]. This latter circuit isconstituted by a circuit line Ina.

The relay II is conditioned for control by the hygrostat I2 only whenthe temperature of the chill room has been lowered to a predeterminedtemperature by operation of compressor 4, condenser Z and evaporator 3as a conventional cooling or refrigerating machine. When, however, thepredetermined temperature controlled by the thermostat 8 is reached, thefunctioning of the thermostat eifects operation of control relay II forcontrol by the hygrostat I2 of the predetermined humidity conditions inthe chill room.

The relay II has a control circuit In therethrough in connection withhygrostat I2 and thermostat 8 including a circuit line I2b from relay IIto the neutral lead Illb. Relay II is supplied with current by a circuitline I lb. The relay I I controls a circuit therethrough which connectsby a circuit line I I with the circuit Illa to the fan Ill. The relay IIalso includes and controls a circuit therethrough which connects by acircuit line I8b with the circuit I8a to motor controlling contactorunit I8. The relay I! also includes and controls an actuating circuitthrough the solenoid operated valve 6 in the condensate return line II)from the air cooled condenser I. This circuit includes a circuit line 6afrom relay I I to one side of solenoid valve 6 and to circuit line B?)from the other side of the solenoid to the neutral lead I 0b.

The system may include an electric motor driven circulating fan or fansI!) included in a circuit constituted by a circuit line Illa betweenrelay 9 and one side of the motors Ill, and a connection from theopposite side of the motor of a fan III to the neutral lead IIlb.

An automatic pressure controlled valve 1 is connected in the coolingwater supply line Ia to the condenser 2 for controlling flow throughthat line. This valve 1 is controlled by a pressure line To fromcompressor 4 in a manner such that upon a predetermined fall of pressurein compressor 4 the valve I is actuated to close lines Ia and thus stopconsumption of water by the water cooled condenser 2, while at anotherpredetermined higher pressure the valve is actuated to open position forsupply of cooling water to the condenser in the normal refrigeratingoperation.

The air cooled condenser or air heater I is provided of such relativelylarge dimensions that during the operation of the system to include theheat pumping cycle the liquefying or condensing temperature ispreferably 5 C. lower than the temperature in the water cooled condenser2, As a result of this fall of pressure resulting from the lowercondensing temperature as referred to above, the water valve I is causedto operate to close the cooling water supply line I to the condenser 2.And in addition, because of this fall of final pressure, the powerrequired by the compressor is also reduced.

With the system of the invention functioning solely as a refrigeratingor cooling cycle to lower the temperature in the chill room or otherspace to be refrigerated, the thermostat 8 has functioned to actuate themaster relay 9 to condition the various circuits controlled thereby tocause operation of the compressor 4, fan or fans It! and the electricalshut-off valve 5, so that, liquid refrigerant is forced from condenser 2through line 20, reservoir I6 and line 3b into the evaporator 3. Thecold evaporation gases are then drawn back through line 3a to thesuction side of compressor 4 for recycling, in the usual manner. In thesystem when. so operated, valve 5 is open while the valve I5 in thecondensate return line I b from the air cooled condenser I is closed,thus effectively shutting off operation of that condenser to function asa heating element.

When, however, the predetermined temperature has been reached in thecold room, the thermostat 8 switches off the master relay 9 and, throughthe circuits as above described. conditions the control relay II foroperation by the hygrostat I 2 upon an increase in the humidity of thecold room. When the predetermined humidity is reached and hygrostat I2effects operation of control relay I I, the system is then caused tofunction partially as a heat pump to condition of the air in the coldroom. The switching on of relay II by hygrostat I2 closes the circuit6a6b through solenoid valve 6 to cause that valve to open. At the sametime valve 5 has been caused to close or partially close, so that hot,compressed gases then circulate through line Ia to air cooled condenserI, and through that condenser to heat the air therein, with theresulting condensate being returned back to reservoir I6 through thereturn line Ib. During such operations, the refrigerating machinefunctions partly as a heat pump and cooperates with the air cooledcondenser for air heater I, so that in the example apparatus hereof, theair in heat exchange relation with the evaporator 3 is first cooledthrough about 3 C, and is then warmed through about 5 C. in thesucceeding air heater I which then functions as the condenser of a heatpump.

The change over from cooling operation solely of the system to anoperation in which the system functions also as a heat pump, andconversely, is effected by means of the master relay 9 and control relayII. These relays are so controlled by the thermostat 8 and hygrostat I2that the predetermined temperature has to be reached in the chill roombefore the thermostat relay 9 sets up the relay I I for control by thehygrostat. Hence, only when the predetermined temperature for which thethermostat 8 has been adjusted is reached in the chill room are thecircuits for setting up the heat pumping function conditioned forcontrol by hygrostat. In this manner, any undesirable raising of thetemperature by the heat pump is prevented. The thermostat 8 controllingrelay 9 effects operation of the system as a refrigerating cycle whilethe hygrostat I2 controls relay II effecting operation of the heat pumpcycle. The change over from operation of the apparatus to perform therefrigerating cycle, to operation of the apparatus to include the heatpump cycle, is effected by the automatic changing over of the twocondensers I and 2 which are connected in parallel. The electricalcontrol shut off valves 5 and 6 are automatically operated to functionfor interrupting the condensation both in the water cooled condenser 2and in the air cooled condenser], these valves being opened and closedby the relays 9 and II which are in turn controlled, respectively, bythe thermostat 8 and the hygrostat 12.

In refrigerating plants comprising a plurality of chill rooms it may bedesirable to perform an air-conditioning only in one or several of theserooms. In this case, a spring-loaded check valve may be used instead ofthe electrical shut-off valve 5. Thereby will be obtained an adjustableincrease of pressure in the Water-cooled condenser 2. Due tothisoverpressure and by opening the valve 6 during the air-conditioningsuch a quantity of gas will be conducted to the air heater I, whichsuffices, when being condensed, for radiating an amount of heat to theroom which is needed to eliminate the refrigerating output of theair-cooler 3 partially or completely.

The time of operation of a refrigerating machine is normally determinedby the demand for cold of the chambers connected thereto. The time ofoperating amounts, if importance is attached to correct humidity of theair, to from 12 to 14 hours per day. With purely thermostatic control,therefore, the idle intervals are about equal in length to the coolingperiods.

During the colder season, and particularly in winter, the demand forcold from the cooling plant falls off considerably, as the temperaturedropis smaller, corresponding to the smaller difference between thetemperature in the chill room and that in the surroundings. In extremefalls of the outside temperature the case may even arise that with knownmethods and cooling installations no cooling at all by tilerefrigerating machine takes place. The shorter the running time of themachine, however, the moister does the chill room become, because theremoval of moisture from the air in the room only takes place during thecooling. Particularly in a meat-storage room, in consequence of thewithdrawal of moisture from the stored contents, after even two hoursinterruption of the cooling the relative humidity of the air in thechill room will rise to over 90 per cent; that is, it will reach a valueat which the meat deteriorates owing to the formation of mould and thedecomposition of protein. The storage of meat for a longer period isonly feasible with a constant humidity of the air in the room of at most75 per cent, that is, a humidity at which the formation of mould isprecluded. In recent cooling installations an attempt has therefore beenmade, by artificially heating the air of the room during the colderseason, to replace the absent heat transmission through the insulationfrom outside, and thereby artificially increase the running time of therefrigerating machine to that value which ensures the air-dryingassociated therewith. With fully automatic electrical refrigeratinginstallations, electrical energy is as a rule adopted as the source ofheat, that is to say, a source of heat which is rather expensive inoperation. Thus for example a cooling plant with a refrigeratingcapacity of 10,000 calories per hour requires a heater of at least 6kilowatts connected load. on an annual average, such heating is switchedon for from 5 to 6 hours per day. For such an installation, therefore,the current consumption per year amounts to about 11,000 kilowatt-hours.A fur-1 ther disadvantage of the electrical heating of chill roomsconsists in the fact that in the vicinity of the heater, in consequenceof the unavoidable thermal radiation, the material that is being cooledis adversely affected. There is also the risk that the cooling elementsmay thaw off during the heating period, a disadvantage that should beobviated, since with the thawing is associated a further increase in thehumidity of the air in the room. In the case of electrically heatedchill rooms the refrigerating machine is controlled, or in other wordsswitched on and off, by the thermostat, and the heating by thehygrostat. This control is associated with serious disadvantages,because the heating, switched on by means of a hygrostat, first has toheat up the air from 1 to 2 degrees centigrade before thether mostat hasovercome its own difference and can switch on the refrigerating plant.During the heating-up time the humidity, which has in any case beenraised, is thereby still further increased. Conversely, notwithstandingthe relative moisture content of the air having been reached, theair-drying will still continue until the heat ac cumulated in the heateris discharged. In both cases, therefore, an over-control is effected inrespect of air-drying and moistening. Great fluetuations in the humidityof the air are however just as injurious as too high or toolow amoisture content.

The method described enables the said disadvantages of the known coolingdevices of fully automatic electrical refrigerating installations to beeliminated; the temperature and humidity to be maintained exactly at theadjusted value without fluctuations; and the economy of the plant to beimproved by from 30 to per cent.

What I claim is:

1. A system for maintaining constant the tem perature and the humidityof a space to be conditioned comprising, in combination, a refrigeratingmachine including, a refrigerant compressor, a liquid-cooled condenser,and a, refrigerant evaporator in heat transfer relation with the spaceto be conditioned; an air-cooled condenser in heat exchange relationwith the space to be conditioned and being connected in parallel withsaid liquid-cooled condenser; means for controlling the discharge ofcondensed refrigerant from said liquid-cooled condenser; means forcutting in and rendering active said air-cooled condenser to cause saidcompressor to function as a heat pump with said air-cooled condenser;temperature control means in the space to be conditioned in operativerelation with said means for cutting out said liquid-cooled condenser;and humidity controlled means in the space to be conditioned inoperative association with said means for cutting in said air-cooledcondenser.

2. A system for maintaining substantially constant the temperature andthe humidity of a space to be air conditioned, comprising, incombination, a refrigerating machine including a refrigerant compressor,a, liquid-cooled condenser, a refrigerant evaporator in heat exchangerelation with the space to be conditioned, and refrigerant lines betweenand connecting said compressor, condenser and evaporator; an aircooled'condenser in heat exchange relation with the space to be conditioned;refrigerant lines connecting said air-cooled condenser directly withsaid compressor for supplying hot, compressed refrigerant gas to saidcondenser; means operable for controlling the operation of said Iliquid-cooled condenser; a thermostat in the space to be air-conditionedfor effecting the operation of said means for controlling theliquidcooled condenser; means for cutting in and rendering active saidair cooled condenser to cause said compressor to supply hot compressedgases thereto and for cutting out and rendering inactive said air-cooledcondenser; an hygrostat in the space to be conditioned for controllingsaid means for cutting in and cutting out said aircooled condenser; andsaid thermostat being operatively connected with said hygrostat forrendering the latter effective for controlling said means for cutting inand cutting out said aircooled condenser only when said thermostat haseffected operation of the means for controlling said liquid-cooledcondenser.

3. A method for air conditioning a chill room by maintainingsubstantially constant the temperature and the humidity of the air inthe room by means of a refrigerating machine, including the steps of;operating the refrigerating machine to perform solely a refrigeratingcycle to cool the air in the room to a predetermined temperature; thenafter attainment of the predetermined temperature, effecting operationof the refrigerating machine to transfer heat therefrom directly to theair in the room until the humidity condition in the room attains apredetermined value or until a predetermined temperature of the air inthe room is attained, whichever is prior; and then repeatingcontinuously the aforesaid steps in the sequence recited to maintainsubstantially constant predetermined temperature and humidity conditionsin the room.

4. A system for maintainin constant the temperature and humidity of aspace to be conditioned, comprising, in combination; a refrigerat ingmachine including a compressor, a liquidcooled condenser, a refrigerantevaporator in heat transfer relation with the space to be conditioned,and refrigerant lines connecting said compressor, condenser andevaporator; an aircooled condenser in heat exchange relation with thespace to be conditioned; refrigerant lines connecting said air-cooledcondenser with said compressor for supplying hot compressed gas to saidair-cooled condenser; means for controlling discharge of condensedrefrigerant from said liquid-cooled condenser; a thermostat in the spaceto be conditioned for controlling the operation of said means forcontrolling said liquidcooled condenser; means for cutting in andcutting out said air-cooled condenser; and an hygrostat in the space tobe conditioned for controlling the operation of said means for cuttin inand cutting out said air-cooled condenser.

5. A system for maintaining constant the temperature and the humidity ofa space to be conditioned, comprising in combination; a refrigeratingmachine including a compressor, a liquidcooled condenser, a refrigerantevaporator in heat exchange relation with the space to be conditioned,and refrigerant lines operatively connecting said compressor, condenserand evaporator; an air-cooled condenser mounted in heat transferrelation with the space to be conditioned; refrigerant lines connectingsaid aircooled condenser in parallel with said liquidcooled condenser; avalve in the refrigerant lines between said liquid-cooled condenser andsaid evaporator adapted to control delivery of condensed refrigerantfrom said liquid-cooled condenser; a valve in the refrigerant line tosaid air-- cooled condenser for closing to cut out and for opening tocut in said air-cooled condenser; a thermostat in the space to beconditioned adapted to control said valve in the refrigerant lines forcontrolling delivery of refrigerant from said liquid-cooled condenser;and a hygrostat in the space to be conditioned for controlling saidvalve in said lines to said air-cooled condenser.

6. In a method for maintaining constant the temperature and the humidityof a space to be refrigerated by means of a refrigerating machine havinga liquid cooled refrigerant condenser, and a refrigerant evaporator andan air cooled refrigerant condenser both in direct heat exchangerelation with the air in the space to be conditioned, the steps of;operating the refrigerating machine to evaporate refrigerant in saidevaporator to thereby cool the air in the space to be refrigerated to apredetermined temperature; then after attainment of the predeterminedtemperature, effecting operation of the machine to supply uncondensedrefrigerant to said air cooled condenser for condensation therein andtransfer of heat to the air in the space to be conditioned until thehumidity condition in the room attains a predetermined value or until apredetermined temperature in the room is attained, whichever is prior;and then repeating continuously the aforesaid steps in the sequencerecited to maintain substantially constant predetermined temperature andhumidity conditions in the room.

'7. A system for maintaining constant the temperature and the humidityof a space to be conditioned, comprising in combination; a refrigeratingmachine including a compressor, a liquidcooled condenser, a refrigerantevaporator in heat exchange relation with the space to be conditioned,and refrigerant lines operatively connecting said compressor, condenserand evaporator; an air-cooled condenser mounted in heat transferrelation with the space to be conditioned; refrigerant lines connectingsaid aircooled condenser in parallel with said liquidcooled condenser; avalve in the refrigerant lines between said liquid-cooled condenser andsaid evaporator adapted to control delivery of condensed refrigerantfrom said liquid-cooled condenser; a valve in the refrigerant line tosaid aircooled condenser for closing to cut out and for opening to cutin said air-cooled condenser; a

thermostat in the space to be conditioned adapted to control said valvein the refrigerant lines for controlling delivery of refrigerant fromsaid liquid-cooled condenser; and a hygrostat in the space to beconditioned for controlling said valve in said lines to said air-cooledcondenser, the thermostat being operatively connected with saidhygrostat to render the latter inoperative when said valve is opened formaximum discharge from said liquid-cooled condenser and to render saidhygrostat operative when said valve is operated to control dischargefrom said condenser.

THEOPHIL EICHMANN.

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